From: Brijesh Singh <brijesh.singh@amd.com>
To: Borislav Petkov <bp@alien8.de>
Cc: brijesh.singh@amd.com, x86@kernel.org,
linux-kernel@vger.kernel.org, kvm@vger.kernel.org,
tglx@linutronix.de, jroedel@suse.de, thomas.lendacky@amd.com,
pbonzini@redhat.com, mingo@redhat.com, dave.hansen@intel.com,
rientjes@google.com, seanjc@google.com, peterz@infradead.org,
hpa@zytor.com, tony.luck@intel.com
Subject: Re: [PATCH Part1 RFC v2 02/20] x86/sev: Save the negotiated GHCB version
Date: Tue, 11 May 2021 13:29:00 -0500 [thread overview]
Message-ID: <36add6ab-0115-d290-facd-2709e3c93fb9@amd.com> (raw)
In-Reply-To: <YJpM+VZaEr68hTwZ@zn.tnic>
On 5/11/21 4:23 AM, Borislav Petkov wrote:
> On Fri, Apr 30, 2021 at 07:15:58AM -0500, Brijesh Singh wrote:
>> The SEV-ES guest calls the sev_es_negotiate_protocol() to negotiate the
>> GHCB protocol version before establishing the GHCB. Cache the negotiated
>> GHCB version so that it can be used later.
>>
>> Signed-off-by: Brijesh Singh <brijesh.singh@amd.com>
>> ---
>> arch/x86/include/asm/sev.h | 2 +-
>> arch/x86/kernel/sev-shared.c | 15 ++++++++++++---
>> 2 files changed, 13 insertions(+), 4 deletions(-)
>>
>> diff --git a/arch/x86/include/asm/sev.h b/arch/x86/include/asm/sev.h
>> index fa5cd05d3b5b..7ec91b1359df 100644
>> --- a/arch/x86/include/asm/sev.h
>> +++ b/arch/x86/include/asm/sev.h
>> @@ -12,7 +12,7 @@
>> #include <asm/insn.h>
>> #include <asm/sev-common.h>
>>
>> -#define GHCB_PROTO_OUR 0x0001UL
>> +#define GHCB_PROTOCOL_MIN 1ULL
>> #define GHCB_PROTOCOL_MAX 1ULL
>> #define GHCB_DEFAULT_USAGE 0ULL
>>
>> diff --git a/arch/x86/kernel/sev-shared.c b/arch/x86/kernel/sev-shared.c
>> index 6ec8b3bfd76e..48a47540b85f 100644
>> --- a/arch/x86/kernel/sev-shared.c
>> +++ b/arch/x86/kernel/sev-shared.c
>> @@ -14,6 +14,13 @@
>> #define has_cpuflag(f) boot_cpu_has(f)
>> #endif
>>
>> +/*
>> + * Since feature negotitation related variables are set early in the boot
>> + * process they must reside in the .data section so as not to be zeroed
>> + * out when the .bss section is later cleared.
> *
> * GHCB protocol version negotiated with the hypervisor.
> */
>
>> +static u16 ghcb_version __section(".data") = 0;
> Did you not see this when running checkpatch.pl on your patch?
>
> ERROR: do not initialise statics to 0
> #141: FILE: arch/x86/kernel/sev-shared.c:22:
> +static u16 ghcb_version __section(".data") = 0;
>
I ignored it, because I thought I still need to initialize the value to
zero because it does not go into .bss section which gets initialized to
zero by kernel on boot.
I guess I was wrong, maybe compiler or kernel build ensures that
ghcb_version variable to be init'ed to zero because its marked static ?
>> static bool __init sev_es_check_cpu_features(void)
>> {
>> if (!has_cpuflag(X86_FEATURE_RDRAND)) {
>> @@ -54,10 +61,12 @@ static bool sev_es_negotiate_protocol(void)
>> if (GHCB_MSR_INFO(val) != GHCB_MSR_SEV_INFO_RESP)
>> return false;
>>
>> - if (GHCB_MSR_PROTO_MAX(val) < GHCB_PROTO_OUR ||
>> - GHCB_MSR_PROTO_MIN(val) > GHCB_PROTO_OUR)
>> + if (GHCB_MSR_PROTO_MAX(val) < GHCB_PROTOCOL_MIN ||
>> + GHCB_MSR_PROTO_MIN(val) > GHCB_PROTOCOL_MAX)
>> return false;
>>
>> + ghcb_version = min_t(size_t, GHCB_MSR_PROTO_MAX(val), GHCB_PROTOCOL_MAX);
> How is that even supposed to work? GHCB_PROTOCOL_MAX is 1 so
> ghcb_version will be always 1 when you do min_t() on values one of which
> is 1.
>
> Maybe I'm missing something...
In patch #4, you will see that I increase the GHCB max protocol version
to 2, and then min_t() will choose the lower value. I didn't combine
version bump and caching into same patch because I felt I will be asked
to break them into two logical patches.
>
next prev parent reply other threads:[~2021-05-11 18:29 UTC|newest]
Thread overview: 62+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-04-30 12:15 [PATCH Part1 RFC v2 00/20] Add AMD Secure Nested Paging (SEV-SNP) Guest Support Brijesh Singh
2021-04-30 12:15 ` [PATCH Part1 RFC v2 01/20] x86/sev: Define the GHCB MSR protocol for AP reset hold Brijesh Singh
2021-04-30 12:15 ` [PATCH Part1 RFC v2 02/20] x86/sev: Save the negotiated GHCB version Brijesh Singh
2021-05-11 9:23 ` Borislav Petkov
2021-05-11 18:29 ` Brijesh Singh [this message]
2021-05-11 18:41 ` Borislav Petkov
2021-05-12 14:03 ` Brijesh Singh
2021-05-12 14:31 ` Borislav Petkov
2021-05-12 15:03 ` Brijesh Singh
2021-04-30 12:15 ` [PATCH Part1 RFC v2 03/20] x86/sev: Add support for hypervisor feature VMGEXIT Brijesh Singh
2021-05-11 10:01 ` Borislav Petkov
2021-05-11 18:53 ` Brijesh Singh
2021-05-17 14:40 ` Borislav Petkov
2021-04-30 12:16 ` [PATCH Part1 RFC v2 04/20] x86/sev: Increase the GHCB protocol version Brijesh Singh
2021-04-30 12:16 ` [PATCH Part1 RFC v2 05/20] x86/sev: Define SNP Page State Change VMGEXIT structure Brijesh Singh
2021-05-18 10:41 ` Borislav Petkov
2021-05-18 15:06 ` Brijesh Singh
2021-04-30 12:16 ` [PATCH Part1 RFC v2 06/20] x86/sev: Define SNP guest request NAE events Brijesh Singh
2021-05-18 10:45 ` Borislav Petkov
2021-05-18 13:42 ` Brijesh Singh
2021-05-18 13:54 ` Borislav Petkov
2021-05-18 14:13 ` Brijesh Singh
2021-04-30 12:16 ` [PATCH Part1 RFC v2 07/20] x86/sev: Define error codes for reason set 1 Brijesh Singh
2021-05-18 11:05 ` Borislav Petkov
2021-04-30 12:16 ` [PATCH Part1 RFC v2 08/20] x86/mm: Add sev_snp_active() helper Brijesh Singh
2021-05-18 18:11 ` Borislav Petkov
2021-05-19 17:28 ` Brijesh Singh
2021-04-30 12:16 ` [PATCH Part1 RFC v2 09/20] x86/sev: check SEV-SNP features support Brijesh Singh
2021-05-20 16:02 ` Borislav Petkov
2021-05-20 17:40 ` Brijesh Singh
2021-04-30 12:16 ` [PATCH Part1 RFC v2 10/20] x86/sev: Add a helper for the PVALIDATE instruction Brijesh Singh
2021-04-30 13:05 ` Brijesh Singh
2021-05-20 17:32 ` Borislav Petkov
2021-05-20 17:44 ` Brijesh Singh
2021-05-20 17:51 ` Borislav Petkov
2021-05-20 17:57 ` Brijesh Singh
2021-04-30 12:16 ` [PATCH Part1 RFC v2 11/20] x86/compressed: Add helper for validating pages in the decompression stage Brijesh Singh
2021-05-20 17:52 ` Borislav Petkov
2021-05-20 18:05 ` Brijesh Singh
2021-05-25 10:18 ` Borislav Petkov
2021-04-30 12:16 ` [PATCH Part1 RFC v2 12/20] x86/compressed: Register GHCB memory when SEV-SNP is active Brijesh Singh
2021-05-25 10:41 ` Borislav Petkov
2021-04-30 12:16 ` [PATCH Part1 RFC v2 13/20] x86/sev: " Brijesh Singh
2021-05-25 11:11 ` Borislav Petkov
2021-05-25 14:28 ` Brijesh Singh
2021-05-25 14:35 ` Borislav Petkov
2021-05-25 14:47 ` Brijesh Singh
2021-05-26 9:57 ` Borislav Petkov
2021-05-26 13:23 ` Brijesh Singh
2021-04-30 12:16 ` [PATCH Part1 RFC v2 14/20] x86/sev: Add helper for validating pages in early enc attribute changes Brijesh Singh
2021-05-26 10:39 ` Borislav Petkov
2021-05-26 13:34 ` Brijesh Singh
2021-04-30 12:16 ` [PATCH Part1 RFC v2 15/20] x86/kernel: Make the bss.decrypted section shared in RMP table Brijesh Singh
2021-04-30 12:16 ` [PATCH Part1 RFC v2 16/20] x86/kernel: Validate rom memory before accessing when SEV-SNP is active Brijesh Singh
2021-05-27 11:49 ` Borislav Petkov
2021-05-27 12:12 ` Brijesh Singh
2021-05-27 12:23 ` Borislav Petkov
2021-05-27 12:56 ` Brijesh Singh
2021-04-30 12:16 ` [PATCH Part1 RFC v2 17/20] x86/mm: Add support to validate memory when changing C-bit Brijesh Singh
2021-04-30 12:16 ` [PATCH Part1 RFC v2 18/20] x86/boot: Add Confidential Computing address to setup_header Brijesh Singh
2021-04-30 12:16 ` [PATCH Part1 RFC v2 19/20] x86/sev: Register SNP guest request platform device Brijesh Singh
2021-04-30 12:16 ` [PATCH Part1 RFC v2 20/20] virt: Add SEV-SNP guest driver Brijesh Singh
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